Conventionally, there has been known a keyboard that can change a layout and a size of a key top (see Japanese Laid-open Patent Publication No. 2014-82099). In this keyboard, when two single-size key tops are replaced with a double-size key top, one slider among two sliders fixed to the double-size key top depresses a contact for key input, and another slider does not depress the contact for key input. By this configuration, the increase of an operation load by the enlargement of the size of the key top is restrained.